This invention relates to electrical interconnect systems such as electrical connectors or the like.
Many types of electrical interconnect systems are employed for interconnecting electrical and electronic systems, and subsystems, and components thereof. In such systems, interconnection is usually accomplished by inserting an electrical pin into an electrical socket thereby electrically coupling two system locations such as circuit junctions, semiconductor device terminals or the like.
An example of one such interconnect system is a pair of components such as electrical connectors each one of which has an insulator body supporting electrical contacts to be mated with the electrical contacts of the other. One of the connectors may have square or round cross-section pins to mate with similar cross-section sockets associated with the other connector. The contacts (pins and/or sockets) may be supported within the channels of an insulative housing such as the connector shown in U.S. Pat. No. 4,682,839 assigned to the assignee hereof, or they may be received through and supported in apertures formed in an insulative substrate. With respect to pins, one end of the pin may extend from the substrate or housing for mating connection with a socket, while the back end of the pin may be joined to a wire of a cable or to an electrical conductor or trace formed in or on the substrate. Alternatively, the back end of the pin may also extend from the substrate for connection to another substrate such as a printed circuit board as seen in U.S. Pat. No. 4,655,517, also assigned to the assignee hereof. With respect to sockets, the mouth of the sockets may be situated adjacent the front wall of the substrate or housing. The back end of the socket may be joined to a wire, conductor or another substrate as in the case of a pin.
As will be appreciated, the electrical contacts must be supported by the pair of connector components in complementary arrangement so that when two connectors are joined together, each pin will be aligned with and be received in a respective socket. To this end, one conventional approach is to position each electrical contact such that its longitudinal axis passes through the intersection of an imaginary square or rectangular grid or matrix on a surface of the substrate to form evenly dispersed rows and columns of pins or sockets. The electrical contacts of a connector must, however, be spaced far enough apart from one another to ensure that there is sufficient insulator housing or substrate material or "real estate" to properly support each contact. To this end, a common arrangement has been to select a square grid having 100 mil (0.100 inch) spacing between adjacent intersections in each row and each column. With a 100 mil by 100 mil square grid arrangement, the centerline of each row of contacts is spaced 100 mil from the next. Furthermore, the centerline or longitudinal axis of each contact in a row is spaced 100 mil from the longitudinal axis of an adjacent contact in that row. This type of arrangement results in a connector having a density of not more than 100 contacts per square inch in that the longitudinal axis of each electrical contact is spaced 100 mil from any adjacent electrical contact in the row and/or column.
As electronic components are made to operate at ever-increasing speeds, and are made in ever smaller dimensions, efforts are needed to increase the density of the contacts in the interconnect system. To this end, various suggestions have been made which increase the density to about 200 contacts per square inch. One suggestion has been to reduce the spacing between contact axes in each row to 50 mil while maintaining spacing between the row centerlines at 100 mil. The result is a rectangular grid with a density of about 200 electrical contacts per square inch. Another suggestion has been to offset every other row to define a diamond-shaped grid with the spacing between contact axes in each row maintained at 100 mils but the spacing between row centerlines reduced to 50 mil. The diamond grid arrangement also provides a density of up to 200 electrical contacts per square inch.
Even greater density is needed. In particular, a density of at least 400 contacts per square inch (e.g., with not more than a 50 mil by 50 mil grid) is desired. Apparently, efforts to reduce contact spacing in both directions, i.e., to a square grid with 50 mil or less spacing, have not met with much success. As is well recognized, pins must have some finite dimension to them so that they retain their structural integrity when in use. Conventionally, such pins are round or square in cross-section and may have a diameter of more than 18 mil and, typically, 25 mil when round or a dimension of more than 25 mil by 25 mil when square. Similarly, the sockets must have a hole diameter about equal to or larger than the cross-section of the connecting end of the pin to be received therein. Sockets may typically also include resilient walls or wiper arms which expand or are urged outwardly from the axis of the socket by the pin as it is inserted into the socket to thereby grip the pin. The resilient arms or expanded walls maintain normal force against the pin to provide the electrical interconnection. However, the area of connector substrate devoted to the socket must take into account such movement or expansion of the socket mechanism. Furthermore, a certain amount of substrate material or real estate must surround the socket so that it is supported for use and isolated from adjacent sockets. Consequently, more than a 50 mil by 50 mil area of connector real estate may be devoted to each socket, thereby placing a lower limit on spacing or substrate real estate between contacts.
There is a connector that achieves a 400 contact per square inch (50 mil by 50 mil) density. However, that connector is believed to be deficient in many respects. The connector is limited to, at most, two rows of contacts. The area outboard of the two rows must be made sufficiently large to accommodate the socket such that addition of a third row of contacts within 50 mil of either of the two rows is not believed to be possible. Moreover, the insulative support real estate outboard of the rows (or outboard of a single row where only one row of contacts is used) must be wider than 50 mil per row of contacts (measured transverse the row). Consequently, the connector itself cannot be "stacked" to simulate a multi-row connector having 50 mil row spacing throughout. Still further, the particular way in which the 400 contact per square inch density is achieved results in extremely high insertion force requirements and tolerance build-up problems which can lead to binding or stubbing. As a practical matter, the number of contacts which may be supported and used by such a connector is believed to be limited to about 50, thus failing to take full advantage of the density of that connector.
Merely reducing the cross-section dimension of the contacts to achieve greater density is not believed to be acceptable as structural integrity of the pins and/or sockets may suffer, especially if such reductions are attempted in an effort to achieve a density of at least 400 contacts per square inch and with a connector having an insulative substrate which is no wider than 50 mil per row of contacts. Thus, it is believed that further increase in contact density with currently available contacts would leave too little substrate material (real estate) to properly support the contacts for their intended use.